Forced convection oven

ABSTRACT

A forced convection oven utilizing two blower rotors mounted on opposed walls of the oven cavity adapted to rapidly and efficiently cook food items. The use of two rotors reduces the space requirements within and without the oven for the forced convection components, reduces the velocity of air required to be circulated within the oven cavity and reduces the air circulation path within the cabinet. The blower rotors are powered by air motors which are not adversely affected by high ambient temperature conditions encountered adjacent the oven.

United States Patent [191 Mutchler FORCED CONVECTION OVEN [75] Inventor: Paul A. Mutchler, University City,

[73] Assignee: The United States of America as represented by the Secretary of the Army, Washington, DC.

[22] Filed: July 5, 1973 [21] Appl. No.1 376,660

[52] US. Cl 126/21 A [51] Int. Cl. F24c 5/16, A2lb 1/26 [58] Field of Search 126/21 A, 273; 219/400 [56] References Cited UNITED STATES PATENTS 3,324,844 6/1967 Huffman 126/21 A 3,411,493 11/1968 Everson et al..,. 126/21 A 3,474,225 10/1969 Leedy 126/21 A X Mar. 19, 1974 2,727,601 4/1973 Klement 126/21 A Primary Examiner-Edward G. Favors Attorney, Agent, or Firm-Edward J. Kelly; Herbert Berl; Lawrence E. Labadini [57] ABSTRACT A forced convection oven utilizing two blower rotors mounted on opposed walls of the oven cavity adapted to rapidly and efficiently cook food items. The use of two rotors reduces the space requirements within and without the oven for the forced convection components, reduces the velocity of air required to be circulated within the oven cavity and reduces the air circulation path within the cabinet. The blower rotors are .powered by air motors which are not adversely affected byhigh ambient temperature conditions encountered adjacent the oven.

6 Claims, 1 Drawing Figure FORCED CONVECTION OVEN The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION This invention relates to convection ovens and, more particularly, to an oven of forced convection design which efficiently circulates heated air within the oven cavity.

It is well known that the cooking efficiency of forced convection ovens is significantly superior to that of conventional convection ovens. ln come instances, the cooking time can be reduced to one-third of the time normally required for cooking the same items and quantity in a conventional oven. While a forced convection oven appears then as a logical choice to satisfy any requirement for high speed cooking equipment, there are a number of significant drawbacks associated with such ovens which generally relate to the bulk or external configuration requirements of such ovens. Forced convection ovens operate by rapidly circulating heated air within the oven cavity and it is this rapid circulation of air which results inthe decrease of time required forcooking. The movement of air within the oven cavity is accomplished by means of a fan or blower located within the cavity and this movement of air within the oven increases the efficiency of heat exchange within the oven. The motor used to drive such a fan or blower is located outside of the oven and constitutes a prominent projection above the .wall of the oven thereby increasing the space requirements for such a cooking device. A further drawback is that presently available electrical drive motors cannot withstand the high ambient temperatures frequently encountered within the vicinity of the oven. Another problem encountered with forced convection ovens is that the high velocity of air required to accomplish the necessary circulation can ripple or otherwise effect the surface appearance of items being cooked at certainlocations within the oven. The present invention, on the other hand, provides a forced convection oven having none of the foregoing drawbacks yet still being capable of rapid and efficient cooking which is of special interest where space requirements are limited and where cooking speed or capacity are prime considerations, as in any type of portable kitchen facility.

SUMMARY The present invention provides anew, useful, compact and unobvious forced convection oven, having two compact blower rotors within the oven cavity located on opposite walls and adapted to circulate heated air within said cavity, having baffle plates adjacent each of said rotors'to direct and control the circulation of BRIEF DESCRIPTION OF THE DRAWING FIG 1 is a partially borken away perspective view of the forced convection oven according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, there :is illustrated a forced convection oven which efficiently circulates heated air within the oven cavity at moderate velocities so as not to adversely affect the surface characteristics of the items being cooked. The oven designated generally as 10, is a typically rectangular, box-dike design, made of sheet metal and appropriately insulated. In more detail, the oven is of double wall construction, having an outer wall or shell 11 and a spaced apart inner wall 12 which defines the oven cavity and is constructed so as to be easily cleaned. Insulation 13 is located betweenthe inner and outer shells. The walls of the oven are further identified as front 14, back 15, top 16,-bottom l7 and side walls 18 and 19. A pair of hinged doors 20 on the front wall 14 permits access to the interior cavity 21 of the oven. The usual complement of racks and shelves, not shown in the drawing, would be contained within the oven cavity.

Thermal energy used to heat the oven may be obtained from any convenient energy source, e.g., by combustion of gaseous or liquid fuels. The oven depicted herein is heated by combustion gases from a liquid fuel-fired burner, not shown, with the combustion gases being delivered to a manifold beneath each of the side walls 18 and 19, and then forced to flow through channels 24 which are in heat conducting relationship with the side walls of the oven cavity, continuing over the top wall 16 and finally exiting through a common exhaust manifold 25 and vent 26. The thermal energy within the combustion gases is conducted via the side and top walls into the cavity 21 of the oven.

. Within the oven cavity 21, there are located two blower rotors 27 which function to circulate heated air at the appropriate or desired circulation rate. The blower rotors consist of a circular plate 28 having a central hub 29 and a rim 30 having a plurality of spaced vanes 31 which function when the rotor is rapidly rotating to force air to flow by centrifugal force. Rotating shafts 33 extend completely through each of the oven side walls and the end of the shaft within the oven cavity is fastened to the hub 29 of the blower rotor. An air motor 33, mounted on the external surface on each of the side walls, is attached to the rotating shaft 32 and functions to turn the shaft which rotates the blower rotor. Air motors are well known in the art, provide a compact, lightweight source of smooth vibrationless power, are not adversely affected by high temperature environments and can be operated at nearly any desired rate of spped. A source of controlled, compressed air, not shown, is all that is required to operate and power the air motor. Afpair of lbaffles 34 are located within the cavity 21 adjacent each blower rotor 27 and serve to direct the flow of heated gas toward the front and back walls of the oven. An opening 35 within the baffle 34 permits air to be drawn from the oven cavity into the blower rotor in turn out the sides of the baffle so that two circular currents of air are created by each rotor. The baffles are attached to the top and bottom walls of the oven so as to allow for removal and cleaning, as necessary.

In operation, the air motor is powered to produce the desired rpm on the shaft and blower rotor. It has been found to be necessary to circulate a minimum of 200 lbs/hr of 400F. oven cavity air to effect an approximate one-third reduction in cooking time and ideally 400 lbs/hr or above to reduce cooking time by about one-half. If one rotor or fan were used to move 400 lbs/hr of 400F. air, the air velocity adjacent the fan would be so high as to affect the surface ofthe food items being cooked and in the case of a soft or flexible item, surface rippling or distortion would occur. By using two rotors, the velocity required to be produced by each rotor is reduced to one-halfof the value required for a single rotor system. Each blower rotor need handle only 200 lbs of 400F. oven cavity air per hour and to accomplish this, the blower rotor has to operate at about 4,200 rpm. The blower rotors are turned on when the food items are introduced into the heated oven and each rotor then circulates the heated air at 200 lbs per hour. With the rotors located as they are on opposite side walls, the air circulation paths within the cavity are exactly half the distance of the air circulation path required to be produced or created by a single fan or blower.

The forced air convection oven of this invention is highly efficient by virtue of its use of two blower rotors to circulate heated air within the cavity at reduced velocities and over shorter circulation paths. The use of air motors eliminates the bulky electrical motors conventionally used to drive a single fan or blower and in addition, the air motors can operate without difficulty in unusually high ambient temperatures of the order of 300 to 900F. An oven as described herein is ideally suited for use in a portable kitchen facility when space is at a premium and where cooking times must be held to a minimum.

1 claim:

1. A forced convection oven having spaced opposed side walls, spaced opposed top and bottom walls and spaced opposed back and front walls which define an oven cavity,

access means located on said front wall to allow access to said oven cavity,

heat conduction means associated with one or more walls of said oven to conduct thermal energy from an external source of thermal energy to the interior of said oven cavity,

air moving means within said cavity and located on each of two opposed walls of said cavity and adapted to circulate air within said cavity,

energy transfer means connected to said air moving means and extending through said oven walls to a source of power outside of said oven walls and adapted to transfer energy from said source of power to drive said air moving means at a controllable rate,

whereby the heated air within said oven cavity is caused to be circulated by each of said air blowing means at the desired velocity.

2. A forced convection oven according to claim 1 wherein each of said air moving means is a rotary blower in combination with a baffle plate, mounted within said cavity and positioned with respect to said rotary blower so as to direct the direction of flow of the rapidly circulating air.

3. A forced convection oven according to claim 2 wherein said energy transfer means is a rotatable shaft and said source of power is an air driven rotary motor.

4. A forced convection oven according to claim 3 wherein said rotary blower is located on the opposed side walls of said oven cavity.

5. A forced convection oven accoding to claim 4 wherein each of said baffle plates direct the flow of air from the rotary blower toward the front and back walls of said oven.

6. A forced convection oven according to claim 5 wherein said baffle plates have'central openings therein which allow air to flow from the oven cavity into the rotary blower. 

1. A forced convection oven having spaced opposed side walls, spaced opposed top and bottom walls and spaced opposed back and front walls which define an oven cavity, access means located on said front wall to allow access to said oven cavity, heat conduction means associated with one or more walls of said oven to conduct thermal energy from an external source of thermal energy to the interior of said oven cavity, air moving means within said cavity and located on each of two opposed walls of said cavity and adapted to circulate air within said cavity, energy transfer means connected to said air moving means and extending through said oven walls to a source of power outside of said oven walls and adapted to transfer energy from said source of power to drive said air moving means at a controllable rate, whereby the heated air within said oven cavity is caused to be circulated by each of said air blowing means at the desired velocity.
 2. A forced convection oven according to claim 1 wherein each of said air moving means is a rotary blower in combination with a baffle plate, mounted within said cavity and positioned with respect to said rotary blower so as to direct the direction of flow of the rapidly circulating air.
 3. A forced convection oven according to claim 2 wherein said energy transfer means is a rotatable shaft and said source of power is an air driven rotary motor.
 4. A forced convection oven according to claim 3 wherein said rotary blower is located on the opposed side walls of said oven cavity.
 5. A forced convection oven accoding to claim 4 wherein each of said baffle plates direct the flow of air from the rotary blower toward the front and back walls of said oven.
 6. A forced convection oven according to claim 5 wherein said baffle plates have central openings therein which allow air to flow from the oven cavity into the rotary blower. 